The WYSIWYG UI is a good feature, although it's not useful for me it is certainly useful for students from other fields who've been riding Word for way too long. You should advertise more to universities and maybe target the non-IT people much more. :)

I believe a more practical feature is adding roles! I mean Editor,Co-Editor, Publisher, Copywriter, Professor, Examiner, Teacher etc. all of these have different jobs, although very similar they do different things. If you give these poor guys a UI or Workflow, that'd be great I think.

Well, if you need a killer argument to sell your product, you'd have to be able to say:

"You write alone or together, we proofread, suggest media, translate, publish, print or schedule submissions for just n$/mo."

Ok, you'd have to integrate external API from ie. commercial online newspapers, qualitative semantically fitting graphics, smart autocompletions with professional "sentence snippets" and so on. Most important thing is to sell it to universities though imho.